1. Field of the Invention
The present invention relates to an optical logic device, and more particularly, to an optical logic device performing a logic operation by utilizing generation of surface plasmon resonance.
The invention also relates to an optical logic circuit and an optical oscillation circuit using the optical logic device.
Furthermore, the invention also relates to an optical memory device storing the modulation status of space-modulated signal light by utilizing generation of surface plasmon resonance.
The invention further relates to an optical operation device determining a difference between two kinds of space modulation states of signal light by utilizing generation of surface plasmon resonance.
2. Description of the Prior Art
Owing to its fast transmission speed, investigations are being widely conducted to apply light to the fields of communication and operation. In these fields, various applications are being studied by utilizing an optical circuit, such as an optical logic circuit.
However, many restrictions have been conventionally applied to the constitution of an optical circuit because an inexpensive optical switching device has not been available, and an optical circuit having a simple constitution has not been realized. More specifically, it has been very difficult to realize a logic device, such as AND and OR devices, as a basic component of an optical circuit, as well as an optical logic circuit and an optical oscillation circuit obtained by combining the same. Furthermore, even when an optical oscillation circuit is realized, it is difficult to obtain one having a sufficiently high oscillation frequency.
The invention has been developed in view of the circumstances described above, and an object of the invention is to provide an optical logic device having a simple constitution that can be produced at a low cost, as well as an optical logic circuit and an optical oscillation circuit, which are inexpensive and have a high operation speed, obtained by combining the same.
The invention relates to an optical logic device performing a logic operation with respect to one or plural input lights, the optical logic device comprising
a dielectric block arranged in such a manner that a driving light is incident on one plane thereof at a total reflection critical angle through an interior thereof,
a metallic film formed over the one plane of the dielectric block, and
an optical functional film, a refractive index of which is changed by irradiation of light, formed over the metallic film in such a manner that the optical functional film is irradiated with a control light.
In the optical logic device according to the invention, the incident angle of the driving light on the one plane of the dielectric block is set, for example, at such an angle that when the optical functional film is irradiated with the control light, the surface plasmon resonance is relatively strongly excited on the metallic film, and when the optical functional film is not irradiated with the control light, the surface plasmon resonance is relatively weakly excited or is not excited. The device of this type is hereinafter called an optical logic device of the mode a.
Contrary to the above, the incident angle of the driving light on the one plane of the dielectric block may be set at such an angle that when the optical functional film is not irradiated with the control light, the surface plasmon resonance is relatively strongly excited on the metallic film, and when the optical functional film is irradiated with the control light, the surface plasmon resonance is relatively weakly excited or is not excited. The device of this type is hereinafter called an optical logic device of the mode b.
The invention provides a NOT circuit using an optical logic device of the mode a. The circuit receives one control light incident on the optical functional film of the optical logic device as an input light, and emits a driving light subjected to total reflection at an interface between the dielectric block and the metallic film as an output light, which is a result of the NOT operation.
The invention also provides an exNOR circuit using an optical logic device of the mode a. The circuit receives two control lights incident on the optical functional film of the optical logic device as input lights, and emits a driving light subjected to total reflection at an interface between the dielectric block and the metallic film as an output light, which is a result of the exNOR operation.
The invention also provides an AND circuit using an optical logic device of the mode b. The circuit receives one control light incident on the optical functional film of the optical logic device and one driving light incident on one plane of the dielectric block as two input lights, and emits a driving light subjected to total reflection at an interface between the dielectric block and the metallic film as an output light, which is a result of the AND operation.
The invention also provides an OR circuit using an optical logic device of the mode b. The circuit receives two control lights incident on the optical functional film of the optical logic device as input lights, and emits a driving light subjected to total reflection at an interface between the dielectric block and the metallic film as an output light, which is a result of the OR operation.
While an optical logic circuit using one optical logic device of the invention has been described above, various optical logic circuits and a flip-flop circuit can be formed by using a plurality of the optical logic devices in such a manner that a driving light subjected to total reflection at an interface between the dielectric block and the metallic film of one optical logic device is incident on the other optical logic device as the control light.
More specifically, the invention provides an exOR circuit comprising two optical logic devices of the mode a, the circuit comprising
one of the optical logic devices arranged as a first optical logic device that receives two control lights incident on an optical functional film thereof as input lights, and
another of the optical logic devices arranged as a second optical logic device that receives a driving light subjected to total reflection at an interface between a dielectric block and a metallic film of the first optical logic device as one control light,
the circuit emitting a driving light subjected to total reflection at an interface between a dielectric block and a metallic film of the second optical logic device as an output light, which is a result of the exOR operation.
The invention also provides a NAND circuit comprising an optical logic device of the mode a and an optical logic device of the mode b, the circuit comprising
the optical logic device of the mode b arranged as a first optical logic device that receives one control light incident on an optical functional film thereof and one driving light before being incident on one plane of a dielectric block as two input lights, and
the optical logic device of the mode a arranged as a second optical logic device that receives a driving light subjected to total reflection at an interface between the dielectric block and a metallic film of the first optical logic device as one control light,
the circuit emitting a driving light subjected to total reflection at an interface between a dielectric block and a metallic film of the second optical logic device as an output light, which is a result of the NAND operation.
The invention also provides a NOR circuit comprising an optical logic device of the mode a and an optical logic device of the mode b, the circuit comprising
the optical logic device of the mode b arranged as a first optical logic device that receives two control lights incident on an optical functional film thereof as input lights, and
the optical logic device of the mode a arranged as a second optical logic device that receives a driving light subjected to total reflection at an interface between a dielectric block and a metallic film of the first optical logic device as one control light,
the circuit emitting a driving light subjected to total reflection at an interface between a dielectric block and a metallic film of the second optical logic device as an output light, which is a result of the NOR operation.
In the optical logic circuits of the invention described above, it is preferred to use plural lights having different wavelengths as the plural lights incident on the optical logic device.
The invention further provides an optical oscillation circuit comprising one or plural optical logic devices of the invention. Specifically, an optical oscillation circuit according to the invention comprises an optical logic device of the mode a, and an optical system, by which a driving light subjected to total reflection at an interface between a dielectric block and a metallic film of the optical logic device is incident on an optical functional film of the optical logic device.
The invention still further provides another optical oscillation circuit comprising an optical logic device of the mode b, an optical device of the mode a arranged in such a manner that an optical functional film of the optical logic device of the mode a receives a driving light subjected to total reflection at an interface between a dielectric block and a metallic film of the optical logic device of the mode b, and an optical system, by which a driving light subjected to total reflection at an interface between a dielectric block and a metallic film of the optical logic device of the mode a is incident on an optical functional film of the optical logic device of the mode b.
In the optical oscillation circuits of the invention described above, it is also preferred to use plural lights having different wavelengths as the plural lights incident on the optical logic device.